Support transparent white font image rec in rapidocr_onnxruntime

python/demo.py

@@ -12,7 +12,7 @@
 engine = RapidOCR()
 vis = VisRes()
 
-image_path = "tests/test_files/test_without_det.jpg"
+image_path = "tests/test_files/black_font_color_transparent.png"
 with open(image_path, "rb") as f:
     img = f.read()
 

python/rapidocr_onnxruntime/utils.py

@@ -208,7 +208,12 @@ def cvt_four_to_three(img: np.ndarray) -> np.ndarray:
         not_a = cv2.cvtColor(not_a, cv2.COLOR_GRAY2BGR)
 
         new_img = cv2.bitwise_and(new_img, new_img, mask=a)
-        new_img = cv2.add(new_img, not_a)
+
+        mean_color = np.mean(new_img)
+        if mean_color <= 0.0:
+            new_img = cv2.add(new_img, not_a)
+        else:
+            new_img = cv2.bitwise_not(new_img)
         return new_img
 
     @staticmethod

python/tests/test_ort.py

@@ -20,6 +20,25 @@
 package_name = "rapidocr_onnxruntime"
 
 
+@pytest.mark.parametrize(
+    "img_name,gt",
+    [
+        (
+            "black_font_color_transparent.png",
+            "我是中国人",
+        ),
+        (
+            "white_font_color_transparent.png",
+            "我是中国人",
+        ),
+    ],
+)
+def test_transparent_img(img_name: str, gt: str):
+    img_path = tests_dir / img_name
+    result, _ = engine(img_path)
+    assert result[0][1] == gt
+
+
 @pytest.mark.parametrize(
     "img_name,gt_len,gt_first_len",
     [